Resilient unit for operation in tension



Feb. 26 1946. C. .1. UNDERwooD 2,395,595

RESILIENT UNIT FOR OPERATION IN TENSION Filed Nov. 25, 1943 PatentedFeb. 26, 1946 RESILIENT UNIT FOR OPERATION 1N TENSION Cyril JamesUnderwood, Cheltenham, England,

vassigrnor to Dowty Equipment Limited, Cheitenham, England applicationNovember 23, 1943, serial No. 511,467 In Great Britain November 17, 19423 Claims.

effectively embodied in a single unit complete initself.

A further object of the invention is the provision of a telescopicresilient unit particularly effestive for employment in aircraft andvehicle suspension systems, in which a resilient device operates intension quite independently of a damping stage to restrain' the plungeragainst excessively violent operation, especially in recoil on relief oftension load operating to extend the resilient device in a telescopicsense.

Another object of the invention is the provision of a satisfactoryshock-absorber in oleopneumatic form, in which complete separation ofthe compressed air or other gas which provides the resilience from theliquid which provides for damping action is effectively achieved withoutthe necessity for incorporating a iloating piston.

A still further object of the present invention is the provision of anoleo-pneumatic shock-absorber. which by utilising space within theplunger which is formed hollow for the purpose increases the volumeavailable for compressed air or other gas over that normally provided,and at the same time simplifies the introduction of the compressed airorother gas.

Yet a further object of the invention is the provision of an eminentlypractical form of damned ,resilient unit of very simple construction, inwhich fluid damping action is provided for quite independently ofresilient operation in tension, which thus enables the resilient meansto be selected at the designers choice.

The manner of achievement of the above and other objects oi theinvention will become apparent from the ensuing description and theaccompanying diagrammatic drawing, which is a sectional side elevationof a damped resilient unit resiliently resistant to loads operating intension and embodying the essential features of the invention.

Referring now to .the drawing, the reference numeral l indicates theouter chamber, preferably one end by means of a closure plug 2 embodyinga pin-joint connection lug t. The other end of of cylindrical form, andwhich is closed at.

they cylinder l is open, and the plunger i operates slidably in thegland iltting, generally indicated-by the reference numeral E. At itsouter end the plunger 4 embodies a pin-joint lug fitting S. Forinstallation, the pin-joint fittings 3 and 6 are Iattached to therelatively sprung and unsprung elements of the suspension system orother means in which the resilient device is required to operate.

Apprommately half-way along the cylinder in an axial sense a partition 1is provided which is suitably packed and glanded, being located in anyconvenient manner, as for example by means of the iixing screws or bolts8 engaged through the wall of the cylinder l. The plunger t operatesslidably through the partition l, which is suitably glanded to preventleakage, and the partition 'I thus operates to subdivide the cylinder iinto a compartment 9 for housing the resilient means and a compartmentIii to enclose damping fluid, usually in the form of oil or otherhydraulic iiuid commonly employed in oleo-pneumatic shock-absorbers anddamping devices generally. l

In Oleo-pneumatic types of shock-absorber the space Ill is lled withliquid through a filler plug i i It will be noted that there are twofiller plugs. and for iilling purposes both may be removed so that onecan serve to let airout of the damping uid compartment I0, while the oilor other damping uid is introduced through the other. The iniiationchamber 9 is illled with air or gas at pressure, and in such cases it isconvenient to form the plunger d hollow and to introduce the air or gasinto the hollow plunger through the innation valve l2, the hollowplunger being in communication with the ination chamber t through asuitably-disposed port I3.

Within the ination chamber t the plunger mounts a piston it which issuitably glanded for operation in the bore of the cylinder i and issecured to the plunger in any convenient manner. It will be realisedthat with the inflation chamber 9 at pressure approach of the piston ittowards the partition 'l is resiliently resisted by the entrapped gas,so thatthe device operates to provide eiiective resilient resistance toloads operating in tension.

Immersed in the damping uid within the space it is a damping head i5which is formed integrally with the plunger, or at any rate lockedagainst axial movement with respect thereto. The damping head preferablyincorporates paci;- ing means so that it operates as a. piston whenmoving with the plunger, causing iiuid to be displaced from side to sideof the head through duid-now ports I6 which communicate with the grooveI1 on that i'ace of they damping head directedtowards the partition l. Aclack valve in the form o! an annulus I8 is provided withilowrestriction ports I9 and operates with limited axial freedom betweenthe ciack valve stop ring 20 on the plunger and the adjacent face of thedamping head I5. The arrangement is such that during extension movementoi' the plunger 4 with respect to the cylinderJ under the iniluence ofloads operating in tension, flow oi damping fluid through the ports I6causes a surge operating to lii't the clack valve annulus I8 oi! thegroove I l, so that in actual fact the'plunger 4 operates forextensionin response to tension 'loads almost entirely against pure resiliencealone. On the other hand, when the damping head I 5 is travellingtowards the partition 'I the surge of liquid tends to close the clackvalve annulus I8 against the groove Il, and thus to confine the flow ofiiuid to the owrestrictlon orifices I9. It therefore follows that,whereas resilient yield of the device under the influence of tensionloads occurs against substantially undamped resilient resistance, therecoil or restoration of the unit to its retracted form is appropriatelydamped.

To avoid subjecting the unit to any supplementary resilience or dampingaction, thespace 2| is in communication with atmosphere through the Dort22.

The construction provides an effective damped resilient unit in verysimple form entirely devoid of any complicated internal mechanism; thehollow plunger 4 merely mounts the piston I4 and the damping head I5.The outer chamber I is in the form of a simple cylinder subdivided bythe partition l. Due to the fact that the plunger embodies no internalmechanism, its cross-section may be kept small, thereby making possiblethe provision of an inflation chamber 9 of large crosssection, which maybe supplemented by the space available in the hollow plunger 4. Thepartition 'I provides for complete isolation of the damping iluid spaceI from the ination chamber 9 so that the oating piston normally providedin preferred types of oleo-pneumatic shock-absorber becomes unnecessary.By reason of the -fact that the damping head l5 and the piston I4 aremovable directly with 'the plunger in both directions. it follows thatthe damping action is entirely dependent on plunger movement, and onceinitiated operates throughout .the -intended range over which damping isto be provided for.

'I'he invention is not of course limited to oleopneumatic types ofshock-absorber or like resilient devices, for it is obvious that theresilience instead of being provided by ainor gas at pressure within thecompartment 9 may be afforded by a spring or otherresilient-compressible medium, or some combination of suitable resilientmeans.

What I claim is: 1. A resilient device comprising a tubular Y chamberone at one end, and partitioned intermediate its ends to deilne aliquid-niled damping compartment adjacent such open end, and anair-filled compression compartment isolated from dthe dampingcompartment adjacent its other end, a plunger closing the chambers openend, and extending therelnto and through the damping compartment andpartition into the compression compartment, a piston carried by saidplunger within the compression compartment, spaced from and cooperatingwith the partition to retain air pressure therebetween, and thereby tourge the plunger into the chamber, and to resiliently resist extension,a damping head carried by said plunger within and subdividing thedamping compartment, and damping means regulating passage of liquidbetween the opposite faces of said head, so arranged as to imposesubstantialy no resistance to extension of the resilient device as aWhole, but to damp l rebound retraction only.

2. A resilient device as in claim 1, wherein the damping head is ported,andvalve means carried by said head and cooperating with said ports andurged towards closed position by rebound movement of the plunger,constitute the damping means to regulate retraction.

3. A resilient device comprising a tubular chamber open at one end, andpartitioned intermediate its ends to deilne a 1iquid-fi11ed dampingcompartment adjacent such open end, and a compression compartment iilledwith air under pressure adjacent its other end, a hollow plunger closingthe chambers open end, and extending thereinto and through the dampingcompartment and ypartition into the compression compartment, a 'pistoncarried by the plunger within the compression compartment, spaced fromand cooperating with the partition to retain pressure therebetween, andthereby to urge the plunger into the chamber, and to resiliently resistextension, the plunger having a port affording communication between itshollow bore and said compression chamber, means at the protruding endYof the plunger for regulating the pressure therein, a damping headcarried by said plunger within 'and subdividing the damping compartment,andV damping means regulating passage of liquid between the oppositefaces o1' said head, so arranged as to impose minimum resistance toextension o! the resilient device as a whole, but to damp reboundretraction.

CYRIL JAMES UNDERWOOD.

